GPs' surgeries should be open from 8am until 8pm, seven days a week, David Cameron said as he announced a £50 million trial to encourage longer opening hours.
Up to half a million patients are expected to be covered by a pilot project in areas across England as the government seeks to improve access and cut the pressure on stretched A&E departments.
Almost one in five patients in a recent NHS survey said inconvenient appointments were a concern, with more than 70% backing weekend and after office hours opening.
Under the scheme being unveiled at the Conservative Party conference in Manchester, the extra cash is being offered to groups of GPs proposing the most effective ways to improve access.
As well as extended surgery hours, ministers hope they will pioneer more effective use of technology - such as carrying out consultations with patients via video calls, email and phone.
Electronic prescriptions, online appointment booking and allowing people to visit a number of different surgeries across an area are also measures being sought from the first wave.
Mr Cameron said: "Millions of people find it hard to get an appointment to see their GP at a time that fits in with their work and family life.
"We want to support GPs to modernise their services so they can see patients from 8am to 8pm, seven days a week.
"We also want greater flexibility, so people can speak to their family doctor on the phone, send them an email or even speak to them on Skype."
The first pilot projects are due to be operating by April 2014 with the hope they will be copied widely across the country.
Officials said the 8am-8pm seven-day hours would not be a requirement for successful bids but made clear that was the expectation.
Similar initiatives are already being tried in some parts of the country - including parts of Manchester, where some surgeries will move to seven-day opening.
Health secretary Jeremy Hunt, who will talk about the initiative in his speech to the conference, said: "We live in a 24/7 society, and we need GPs to find new ways of working so they can offer appointments at times that suit hard-working people.
"Cutting-edge GP practices here in Manchester are leading the way, and we want many more patients across the country to benefit."
Professor Steve Field, Chief Inspector for General Practice, said: "This move towards seven day services is great news for patients, and should be embraced by GPs. I want to see brilliant access to GP services for patients across the country, and will be assessing this in each practice I inspect."
Dr Charles Alessi, of the National Association of Primary Care, said: "This has the potential to be the most exciting development in primary care in the last decade.
"It is an opportunity for doctors to be the good family doctors they want to be while working with everyone in the system to deliver better care for everyone, especially those most in need."
Shadow health secretary Andy Burnham said: "David Cameron and the Tories are taking the NHS backwards and this announcement is a major admission of failure and a U-turn of fairly epic proportions.
"Under the Tories, hundreds of GP surgeries are shutting their doors earlier after David Cameron scrapped Labour's successful extended opening scheme.
"Patients are also finding it harder to get appointments, and turning to A&E instead, after he removed Labour's guarantee of an appointment within 48 hours.
"So I sincerely hope Jeremy Hunt isn't expecting applause on GP hours given how they have taken the NHS backwards from the position they inherited from Labour.
"An apology for the inconvenience they have caused to millions would be more appropriate.
"I also hope he won't claim that this will solve David Cameron's A&E crisis. It is the collapse of social care that is driving vulnerable older people into hospital in ever greater numbers and this is the crisis they continue to neglect."